1. Field of the Invention
The present invention relates to perpendicular recording heads used in hard disk drives.
2. Background Information
Hard disk drives contain a plurality of magnetic heads that are coupled to rotating disks. The heads can magnetize and sense the magnetic fields of the disks to write and read data, respectively. The heads each have an air bearing surface that cooperates with a flow of air generated by the rotating disks to create an air bearing. The air bearing prevents mechanical wear between the head and the disk.
The heads magnetize the disk in either a horizontal direction parallel with the disk surface, of a vertical direction perpendicular to the surface of the disk. Vertical recording occupies less surface space and thus allows for increased disk capacity.
Vertical recording heads include a write pole that emanates a magnetic field. The poles typically extend from a yoke. The poles and yoke are integrally formed during the fabrication of the head.
As shown in FIG. 1, the generation of a write current will create a magnetic flux 1 that is vertically aligned with a yoke 2 of a head. When the write current is terminated there is a residual magnetism in the yoke. As shown in FIG. 2, because of the crystalline structure of the yoke 2, the residual magnetism 3 has components in the vertical direction. This vertical magnetism can cause yoke domain lock up. It is possible to reduce domain lock-up by forming an anti-ferromagnetic layer in the yoke. But this would require a sputtering process and would limit the type of manufacturing processes that can be used to fabricate the heads. It would be desirable to provide a yoke design that reduce domain lock-up and would allow the head to be fabricated with different manufacturing processes.